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Ecological Determination of the New Ctenophora-Beroe ovata lnvasion in the Black Sea
Asen S. Konsutov, Lyudmila T. Kamburska
fnstitute of Oceanology, Bu/garian Academy of Sciences (Varna)
Inlroduction. In results of the high Black Sea environment which ensures the "lJ \ lphication and antropic impact during best conditions for development and the last twcnty years [15] the Black Sea reproduetion ofthc invadcr M.leidyi. Despite , , 1 1llL'S favourable for the dcvclopmcnt of of the annual and seasonal fluctuation this many in vaders (Zat ze v, Mam a e v, species has been thc dominant component I qq7). The stabie settiement of some afthem in the B!ack Sea ecosystem during the last leads dircctly to drastic changes in the 10 years with maximal abondance in plankton fauna diversity and its quantitativc 1988-1989 (B o g dan o va, Kon s u I o v, development (Kon su I ov, Kam burska, 1993) and minimal abondance in 1991-1992 1997) and indirectly influences the othcr (Konsulov, Kamburska, 1997). parts in the food chain. This concerns in Feeding on zooplankton M leidyi appears great extent the representatives of as an important rival of the pelagic fish, Ctenophora which are important carnivores which results in a decrease of !heir in planktonic food ebains (Frase r, 1962). commercial resources (Ne Is on, 1925). On Until1985 only one reprcscntative of class Oenophora was known as a part of the Black sea plankton composition-Pleuro/;>rachia pi leus ( =Pleurobrachia rhodopis). This species has never had mass development (Kon s u I o v, 1991). In spring of 1986, 20-30 miles east from Cape Emine, a new one for the time being species of Ctenophora was identified as Mnemiopsis leidyi (Kon s u I o v, 1989). M leidyi has arrived through ship ballast waters from North Atlantic (Vin o g rad o v, 1989 et al.). The reason fortbis species setticment and its development into thc Black Sea basin Fig. 1. Beroe ovata with engulfed individual is the high dcgree of eutrophication of the of Mnemiopsis leidyi -196- the other hand elimination of herbivorous to be exclusively carnivorous on other zooplankton ( especially Copepoda) ctenophores (G ree v e, 1970). Nelson iocrcases the phytoplankton abundance and (Ne Is on, 1925) reports that Beroe ovata biomass (De aso n, Sm a y d a, 1982) feects only on M. leidyi species. Our respectively to a high level of eutrophication. investigation reveal that from 2 to Because of the serious disturbances in the 7 individuals ofM.leidyiwith size 10-20 mm pelagic ecosystem caused after the mass have been discovered in the guts of the live development of this species reaching tata! samples of Beme ovata. Pieces of thc prey biomass more than 5 kg/m2 (M a I as he v, with size 10-40 mm were also found as well Archip o v, 1992) GESAMP outline a as fragments of its sexual arches. Thc strategy for its control in the Black Sea underwater photographs which helped for (GESAMP, 1997). One of the proparsals is the identification of the species from class to apply a biologica! control through Ctenophora completely confirmed the introduetion of its predator of the genus results of the Iabaratory observations for the Beroe. This item has advantages and preserree of M. leidyi in Beroe ovata 's disadvantages. This measure is unnecessary stomach contcnts [Fig. 1]. If the prey is because of the natural invasion of Beroe smaller than theBeroe ovata, it is complctely ovata in the Black Sea. In October 1997, in engulfed. Small individuals of Beroe cut with the vicinity of Shabla, a new species lips parts from the tissue of the M. leidyi belonging to class Ctenophora and identified (S wanberg, 1970). as Beroe ovata was located. The technica! mechanism for transfer of The aim of this paper is to present the main larvae and adult rcprcscntatives of M leidyi reason for the migration of Beroe ovata into and Beroe ovata is one and the same-ballast the Black Sea waters. Up to now this waters. Despite of this !heir invasion did nol predatory species has not been reported for occur simultaneously but within a time gap the basin's fauna. of 10 years. Materials and Methods. The samples for The analysis of the data referring analysis and identification were collccted by zooplankton state, M. leidyi quantity and means of SCUBA di ving technique. Species eutrophication degree shows that in 1986 were gathered in a glass vessel and moved when M. leidyi was discovered in the Black live to the laboratory. During sampling Sea waters, the zooplankton biomass was operations rcpresentatives of the species 192.36 mg/m3 and the number of ctcnophora wcrc shot with underwater camera in their was 8 ind/m3 In 1990 the zooplankton natural environment as they move and eat. biomass decreased to 135.84 mg!m'and thc They wcre identified under Iabaratory number ofM. leidyi increased to 85-150 ind/ conditions after observations of live m3 (Bogdanova, Konsulov, 1993). individuals and species fixed in 4 % An increasing trend of zooplankton biomass formaJin salution and 3 % gluteraldchyde. (a bout 210 mg/m3) was noticed after 1992 Results and Discussion. The results of when the number of M. leidyi was very 3 morphostructural analysis of the Ctenophora low-6 ind/m • In the period 1995-1997 its allow us to assume that this is a ncwcorner average abundance was 277 ind/m' in the Black Sea known as Beroe ovata (Konsulov, Kamburska, 1997). species. lts body is egg -shaped with well Under these ecological and trapbic conditions expressed mouth-eireling rim. Ciliated beits of the Black Sea shallow shelf zone off the are laid meredionally and Jinked with Bulgarian coast the same year we have crosswise archcs. discovered adult and juvenile stages of Beme lt is well known ,that the species of the ovata. The reason for this is the highM. leidyi genusBeroe have previously been considered abondance which Beroe ovata uses to feed -197- on, givc us cnough grounds to assumc that considerations rise some questions : whether the invasion of the new for the Black Sca wolud settie permancntly and whcthcr a Ctenophora is trophically determined. species feeding on it will migrate in the Black Eliminating one of the reason for a high Sea, because local predators of Beroe ovata level of eutrophication-Mnemiopsis leidyi, thc are not known? new ctenophora species Beroe ovata could Acknowledgments. The authors are grateful reach high biomass.This can lead to a new to our colleague the onderwater photographer disturbancc in thc Black Sca ccosystcm as Eng. Lyubomir Klisurov for thc materials and mass development of ctenophores drastically photos. We would like to thank the staff of modifies the structurc of an otherwisc stabie "Marine ecology and bîology" Department, community (Bis hop, 1967). The ahove JO-BAS for the useful comments.
References Bi shop, J. W. 1967. Feeding ratcs of thc thc Bulgarian Coast. D.Sc. Thesis (in Oenophore Mnemiopsis leidyi.-ln: Bulgarian). Konsulov, A., L. Kamburska. Chcsapcakc Sci, 8, 259-264. Bogdanova, D., 1997. Scnsitivity to anthropogenic factors of A. Konsulov. 1993. On the distribution of the plankton fauna adjacent to the Bulgarian thc ncw Ctcnophora species Mnemia coast of the Black Sea.-ln: NATO AS! Mccradyi in the Black Sea along the Series, 2/27, 95-104. Malashev, V. 1., Bulgarian coastlinc in the summer of Archipov, A. G. 1992. The Ctenophore 1990.-In: Comptes rendus de !'Academie Mnemiopsis leülyi in the West part of the bulgare des Scicnces, no 46, 3, 71-74. Black Sea. Hydrobiology Jurn. IBSS, 28/1, Deason, E. and Smayda, T. J. 34-39. Nelson, T. C. 1925. On thc 1982. Oenophore-zooplankton-phytoplankton occurrence and food habits of ctenophores interactions in Narragansett Bay, Rhode in the New Jersey inland coastal watcrs.-In: Island, USA during 1972-1977.-In: Biol. Bull, 48: 92-111. Prodanov, K. et al. J. Plankton Res, 4, 203-217. Fraser, H. F. 1997. Environmental management of fish 1962. The rople of Ctenophores and salps resources in the Black Sea and their rational in zooplankton production and standing cxploitation.-In: F ~:-Studies and reviews, erop. Rapp. P-v. Reun.-In: Cons. perm. int. ?68. Swanberg N. 1970. The feeding E> AceH C. KoHcyAoB, fl10gMu11a T. KaM6ypcKa li1Hcmumym no oKeaHolloeuR, SAH (BapHa) (Pea10Me) IIpe3 nocne,u:HHTe .usaneceT ro.rU1HH B Beroe H H.llCHTHciJM:u;HpaH OT Hac KaTa Beroe pe3yrrTaT Ha IIOBIIllleHaTa eYTpoqmKa!llUI ovata. To311 XHIIJ,HHK He e C'b06llJ,aBaH .n;o H 3HTpüliOfCHHO Bb3;:J;Ci1CTBHC qepHOMOp cera 3a flocmvnuAa Ha 01.03. 98 2.